| 摘要 |
PURPOSE: A charge pump of a phase locked loop is provided to reduce jitter and skew even with a short width of the pulse input by having the constant current source turned on always and flowing the current to other paths when the switch is off. CONSTITUTION: In the charge pump of a phase locked loop, the first constant current source(IUP) is connected to the power source voltage(VDD). The second constant current source(IDN) is connected to the ground(GND). The first switch(S1) operates to the first control signal(UP) and comes between the first constant current source(IUP) and the output node. The second switch(S2) operates to the second control signal(DN) and comes between the output node and the second constant current source(IDN). The third switch(S3) operates to the inverted signal(DNB) of the first control signal(DN) and comes between the first resistor(R1) and the first constant current source(IUP). The fourth switch(S4) operates to the inverted signal(UPB) of the second control signal(UP) and comes between the second resistor(R2) and the second constant current source(IDN). The second resistor(R2) comes between the power source voltage(VDD) and the fourth switch(S4).
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